The backnailing is only done wherever possible. Like runs longer than 12 or 16 ft, (do both corners first, then fill in the middle). Or for short runs that go to an outside corner, like offsets. If any joint needs to be completed aloft, I prefer it to be an outside corner rather than an inside one. On one piece runs with a moulding that can not be coped, simply cut it a smidge longer and spring it in. It will look great forever.
All offsets, and short jogs should be pre-assembled completely before going up, both inside and outside corners.
If I am mitering, wherever possible, I will backnail all my inside joints. It avoids having to shim behind an inside mitre to make it right. Difficult to do with short wall to wall runs, but not impossible if there is a door or window to poke it through for a minute. This method is only for production crews of 2 because you need help raising the backnailed moulding if it extends out in two or even three directions. It looks kind of silly when three guys are lifting three pieces of crown moulding, but it only takes a few seconds and it turns into quite a dance production when doing "production" finish carpentry.
I think that coping was invented by a guy who was stuck working alone.
I was a carp sub at a hotel-condo conversion a few years back, and ran crown in 500 one and 2 bedroom units with one other carpenter and only one chopsaw. One floor of 25 units per week including hallway. It was quite a dance. But that's another post altogether.
I apologize for drifting this thread off it's original course. Let's get back to coping.
I recently did a series of double-end crown copes in a house where a customer decided after the wall cabs were hung and crowned, that he wanted continuous crown rather than it dying to the wall wherever the wall cabinets ended. Needless to say, he was impressed that I didn't disturb the existing crown and a little more educated as far as woodwork goes. "Coped joint " was a major part of his vocabulary for a few days following.